Anopheles gambiae s.s. is the primary mosquito vector of malaria is Africa. As a prelude to the evaluation of strategies for malaria control based on the concept of replacement of vector populations with mosquitoes unable to transmit the malaria parasite, we are examining, in depth, the genetic and biologic structure of vector population in a series of distinct ecological zones in Mali (West Africa). To facilitate these studies, we are using the tools of molecular genetics directed at microsatellite polymorphisms, restriction length polymorphisms (RFLPs), and ribosomal and mitochondrial DNA. Field studies of vector populations using these techniques will be conducted at the Malaria Research and Training Center recently established in Bamako, Mali, in collaboration with staff of the National School of Medicine and Pharmacy of Mali. In addition, studies on larval ecology and nutrition of An. gambiae in Mali seek to identify microorganisms in the diet which might serve as carriers of genes coding for the production of biologically active insecticides for use in larval control programs.